I think you mean this: "When will the wheel be finished? At the moment, we just need a deadline."

There are two sentences there. Each is correct. I understand each on its own. But together? What are you trying to say? What is the timeline to do with the wheel? Could you explain, please?

deadline : a time or date by which a project must be completed. timeline : a schedule or plan showing each point of a project for a nuclear plant: external construction of tower 1 should be completed by March 2015, tower 2 by August, the reactor wont be completed until around November or December. The deadline is January 15 2016.